an irritant – a substance that directly damages the outer layer of skin

an allergen – a substance that causes your immune system to respond in a way that affects the skin

Irritant contact dermatitis

Irritant contact dermatitis may be caused by frequent exposure to a weak irritant, such as soap or detergent. It may also develop if you've been in contact with a stronger irritant for a short while.

You're at an increased risk of irritant contact dermatitis if you also have atopic eczema, which is the most common form of eczema.

Common irritants include:

soaps and detergents

antiseptics and antibacterials

perfumes and preservatives in toiletries or cosmetics

solvents

oils used in machines

disinfectants

acids and alkalis

cement

powders, dust and soil

water – especially hard, chalky water or heavily chlorinated water

many plants – such as Ranunculus, spurge, Boraginaceae and mustards

If you already have irritant contact dermatitis symptoms, they can be made worse by heat, cold, friction (rubbing against the irritant) and low humidity (dry air).

Exposure at work

You may be more at risk of irritant contact dermatitis if you work with irritants as part of your job, or if your job involves a lot of wet work.

If you develop the condition because of a substance you work with, it may be referred to as occupational irritant dermatitis.

This type of dermatitis is more common in certain occupations, including:

agricultural workers

beauticians and hairdressers

chemical workers

cleaners

construction workers

cooks and caterers

metal and electronics workers

health and social care workers

machine operators

mechanics and vehicle assemblers

Allergic contact dermatitis

The first time you come into contact with an allergen, your body becomes sensitised to it, but doesn't react to it. It's only when you're exposed to the substance again that your immune system reacts and causes the skin to become red and itchy.